Question 1

What do we mean by the singularity of a black hole?

Accepted Answer

A) It is the "point of no return" of the black hole; anything closer than this point will not be able to escape the gravitational force of the black hole. 
B) The term is intended to emphasize the fact that an object can become a black hole only once, and a black hole cannot evolve into anything else. 
C) It is the edge of the black hole, where one could leave the observable universe. 
D) It is the center of the black hole, a place of infinite density where the known laws of physics cannot describe the conditions. 
A) It is the "point of no return" of the black hole; anything closer than this point will not be able to escape the gravitational force of the black hole. 
B) The term is intended to emphasize the fact that an object can become a black hole only once, and a black hole cannot evolve into anything else. 
C) It is the edge of the black hole, where one could leave the observable universe. 
D) It is the center of the black hole, a place of infinite density where the known laws of physics cannot describe the conditions.

Question 2

From a theoretical standpoint, what is a pulsar?

Accepted Answer

A) a star that is burning iron in its core 
B) a binary system that happens to be aligned so that one star periodically eclipses the other 
C) a neutron star or black hole that happens to be in a binary system 
D) a rapidly rotating neutron star 
E) a star that alternately expands and contracts in size 
A) a star that is burning iron in its core 
B) a binary system that happens to be aligned so that one star periodically eclipses the other 
C) a neutron star or black hole that happens to be in a binary system 
D) a rapidly rotating neutron star 
E) a star that alternately expands and contracts in size

Question 3

Prior to 1991, most astronomers assumed that gamma- ray bursts came from neutron stars (with accretion disks)within the Milky Way Galaxy. How do we now know that this hypothesis was wrong?

Accepted Answer

A) Theoretical work has proven that gamma rays cannot be produced in accretion disks. 
B) Observations from the Compton Gamma- Ray Observatory showed that gamma- ray bursts occur too frequently to be attributed to neutron stars. 
C) Observations from the Compton Gamma- Ray Observatory showed that gamma- ray bursts come randomly from all directions in the sky. 
D) We now know that gamma- ray bursts come not from neutron stars but from black holes. 
E) Observations from the Compton Gamma- Ray Observatory allowed us to trace gamma- ray bursts to pulsating variable stars in distant galaxies. 
A) Theoretical work has proven that gamma rays cannot be produced in accretion disks. 
B) Observations from the Compton Gamma- Ray Observatory showed that gamma- ray bursts occur too frequently to be attributed to neutron stars. 
C) Observations from the Compton Gamma- Ray Observatory showed that gamma- ray bursts come randomly from all directions in the sky. 
D) We now know that gamma- ray bursts come not from neutron stars but from black holes. 
E) Observations from the Compton Gamma- Ray Observatory allowed us to trace gamma- ray bursts to pulsating variable stars in distant galaxies.

Question 4

Which of the following is closest in mass to a white dwarf?

Accepted Answer

A) the Earth 
B) the Sun 
C) the Moon 
D) Jupiter 
A) the Earth 
B) the Sun 
C) the Moon 
D) Jupiter

Question 5

What is the ultimate fate of an isolated white dwarf?

Accepted Answer

A) As gravity overwhelms the electron degeneracy pressure, it will explode as a nova. 
B) It will cool down and become a cold black dwarf. 
C) As gravity overwhelms the electron degeneracy pressure, it will explode as a supernova. 
D) The electron degeneracy pressure slowly overwhelms gravity and the white dwarf evaporates. 
E) As gravity overwhelms the electron degeneracy pressure, it will become a neutron star. 
A) As gravity overwhelms the electron degeneracy pressure, it will explode as a nova. 
B) It will cool down and become a cold black dwarf. 
C) As gravity overwhelms the electron degeneracy pressure, it will explode as a supernova. 
D) The electron degeneracy pressure slowly overwhelms gravity and the white dwarf evaporates. 
E) As gravity overwhelms the electron degeneracy pressure, it will become a neutron star.

Question 6

Briefly describe what you would see if your friend plunged into a black hole.

Accepted Answer

As he approached the black hole, he woul

Question 7

How does a black hole form from a massive star?

Accepted Answer

A) A black hole forms when two massive main- sequence stars collide. 
B) If enough mass is accreted by a white dwarf star that it exceeds the 1.4 solar mass limit, it will undergo a supernova explosion and leave behind a black- hole remnant. 
C) If enough mass is accreted by a neutron star, it will undergo a supernova explosion and leave behind a black- hole remnant. 
D) Any star that is more massive than 8 solar masses will undergo a supernova explosion and leave behind a black hole remnant. 
E) During a supernova, if a star is massive enough for its gravity to overcome neutron degeneracy pressure in the core, the core will collapse to a black hole. 
A) A black hole forms when two massive main- sequence stars collide. 
B) If enough mass is accreted by a white dwarf star that it exceeds the 1.4 solar mass limit, it will undergo a supernova explosion and leave behind a black- hole remnant. 
C) If enough mass is accreted by a neutron star, it will undergo a supernova explosion and leave behind a black- hole remnant. 
D) Any star that is more massive than 8 solar masses will undergo a supernova explosion and leave behind a black hole remnant. 
E) During a supernova, if a star is massive enough for its gravity to overcome neutron degeneracy pressure in the core, the core will collapse to a black hole.

Question 8

A white dwarf supernova leaves behind

Accepted Answer

A) a newborn star. 
B) a white dwarf. 
C) nothing. 
D) a neutron star or black hole. 
A) a newborn star. 
B) a white dwarf. 
C) nothing. 
D) a neutron star or black hole.

Question 9

What would happen if a small piece of neutron star material (say the size of a paper clip)struck the Earth?

Accepted Answer

The extremely dense material could not b

Question 10

Which of the following best describes why a white dwarf cannot have a mass greater than the 1.4- solar- mass limit?

Accepted Answer

A) White dwarfs are made only from stars that have masses less than the 1.4- solar- mass limit. 
B) Electron degeneracy pressure depends on the speeds of electrons, which approach the speed of light as a white dwarf's mass approaches the 1.4- solar- mass limit. 
C) The upper limit to a white dwarf's mass is something we have learned from observations, but no one knows why this limit exists. 
D) White dwarfs get hotter with increasing mass, and above the 1.4- solar- mass limit they would be so hot that even their electrons would melt. 
A) White dwarfs are made only from stars that have masses less than the 1.4- solar- mass limit. 
B) Electron degeneracy pressure depends on the speeds of electrons, which approach the speed of light as a white dwarf's mass approaches the 1.4- solar- mass limit. 
C) The upper limit to a white dwarf's mass is something we have learned from observations, but no one knows why this limit exists. 
D) White dwarfs get hotter with increasing mass, and above the 1.4- solar- mass limit they would be so hot that even their electrons would melt.

Question 11

Imagine comparing a 1.2 solar mass white dwarf to a 1.0 solar mass white dwarf. Which of the following must be true?

Accepted Answer

A) The 1.2 solar mass white dwarf has a higher surface temperature. 
B) The 1.2 solar mass white dwarf is supported by neutron degeneracy pressure; the 1 solar mass white dwarf is supported by electron degeneracy pressure. 
C) The 1.2 solar mass white dwarf has a smaller radius. 
D) The 1.2 solar mass white dwarf has a lower surface temperature. 
E) The 1.2 solar mass white dwarf has a larger radius. 
A) The 1.2 solar mass white dwarf has a higher surface temperature. 
B) The 1.2 solar mass white dwarf is supported by neutron degeneracy pressure; the 1 solar mass white dwarf is supported by electron degeneracy pressure. 
C) The 1.2 solar mass white dwarf has a smaller radius. 
D) The 1.2 solar mass white dwarf has a lower surface temperature. 
E) The 1.2 solar mass white dwarf has a larger radius.

Question 12

Evidence that Pulsars are Neutron Stars: Suppose a friend of yours insists that pulsars are artificial time- signals constructed by aliens. List and explain all of the observational evidence that pulsars are actually natural phenomena, namely rapidly spinning neutron stars.

Accepted Answer

There is overwhelming evidence that puls

Question 13

A 10 solar mass main sequence star will produce which of the following remnants?

Accepted Answer

A) neutron star 
B) black hole 
C) white dwarf 
D) none of the above 
A) neutron star 
B) black hole 
C) white dwarf 
D) none of the above

Question 14

Which statement concerning black hole masses and Schwarzschild radii is not true?

Accepted Answer

A) In a binary system with a black hole, the Schwarzschild radius depends on the distance from the black hole to the companion star. 
B) Even an object as small as you could become a black hole if there were some way to compress you to a size smaller than your Schwarzschild radius. 
C) The more massive the black hole, the larger the Schwarzschild radius. 
D) For black holes produced in massive star supernovae, Schwarzschild radii are typically a few to a few tens of kilometers. 
A) In a binary system with a black hole, the Schwarzschild radius depends on the distance from the black hole to the companion star. 
B) Even an object as small as you could become a black hole if there were some way to compress you to a size smaller than your Schwarzschild radius. 
C) The more massive the black hole, the larger the Schwarzschild radius. 
D) For black holes produced in massive star supernovae, Schwarzschild radii are typically a few to a few tens of kilometers.

Question 15

What is an accretion disk?

Accepted Answer

A) any flattened disk in space, such as the disk of the Milky Way Galaxy 
B) a disk of material found around every white dwarf in the Milky Way Galaxy 
C) a disk of hot gas swirling rapidly around a white dwarf, neutron star, or black hole 
D) a stream of gas flowing from one star to its binary companion star 
A) any flattened disk in space, such as the disk of the Milky Way Galaxy 
B) a disk of material found around every white dwarf in the Milky Way Galaxy 
C) a disk of hot gas swirling rapidly around a white dwarf, neutron star, or black hole 
D) a stream of gas flowing from one star to its binary companion star

Question 16

According to our modern understanding, what is a nova?

Accepted Answer

A) a rapidly spinning neutron star 
B) the sudden formation of a new star in the sky 
C) an explosion on the surface of a white dwarf in a close binary system 
D) the explosion of a massive star at the end of its life 
A) a rapidly spinning neutron star 
B) the sudden formation of a new star in the sky 
C) an explosion on the surface of a white dwarf in a close binary system 
D) the explosion of a massive star at the end of its life

Question 17

Light escaping from white dwarfs will show a gravitational redshift.

Accepted Answer

A) True 
 B)False

Question 18

What is the evidence that gamma- ray bursts originate from beyond the Milky Way Galaxy?

Accepted Answer

Gamma- ray bursts are distributed unifor

Question 19

Which of the following is closest in size (radius)to a neutron star?

Accepted Answer

A) a basketball 
B) the Earth 
C) a city 
D) the Sun 
E) a football stadium 
A) a basketball 
B) the Earth 
C) a city 
D) the Sun 
E) a football stadium

Question 20

What evidence suggests that long gamma ray bursts originate from supernovae of stars massive enough to form black holes?

Accepted Answer

A) Rapid observations in other wavelengths show that some gamma ray bursts coincide with points showing typical supernova light curves. 
B) Some gamma ray bursts have been found to originate with galaxies that are actively forming stars, and would thus have a few very massive (but short lived)stars. 
C) The locations of gamma ray bursts suddenly begin blocking light from more distant stars. 
D) A and B 
E) B and C 
A) Rapid observations in other wavelengths show that some gamma ray bursts coincide with points showing typical supernova light curves. 
B) Some gamma ray bursts have been found to originate with galaxies that are actively forming stars, and would thus have a few very massive (but short lived)stars. 
C) The locations of gamma ray bursts suddenly begin blocking light from more distant stars. 
D) A and B 
E) B and C

What do we mean by the singularity of a black hole?

From a theoretical standpoint, what is a pulsar?

Prior to 1991, most astronomers assumed that gamma- ray bursts came from neutron stars (with accretion disks)within the Milky Way Galaxy. How do we now know that this hypothesis was wrong?

Which of the following is closest in mass to a white dwarf?

What is the ultimate fate of an isolated white dwarf?

Briefly describe what you would see if your friend plunged into a black hole.

How does a black hole form from a massive star?

A white dwarf supernova leaves behind

What would happen if a small piece of neutron star material (say the size of a paper clip)struck the Earth?

Which of the following best describes why a white dwarf cannot have a mass greater than the 1.4- solar- mass limit?

Imagine comparing a 1.2 solar mass white dwarf to a 1.0 solar mass white dwarf. Which of the following must be true?

Evidence that Pulsars are Neutron Stars: Suppose a friend of yours insists that pulsars are artificial time- signals constructed by aliens. List and explain all of the observational evidence that pulsars are actually natural phenomena, namely rapidly spinning neutron stars.

A 10 solar mass main sequence star will produce which of the following remnants?

Which statement concerning black hole masses and Schwarzschild radii is not true?

What is an accretion disk?

According to our modern understanding, what is a nova?

Light escaping from white dwarfs will show a gravitational redshift.

What is the evidence that gamma- ray bursts originate from beyond the Milky Way Galaxy?

Which of the following is closest in size (radius)to a neutron star?

What evidence suggests that long gamma ray bursts originate from supernovae of stars massive enough to form black holes?

A Modern View of the Universe

Discovering the Universe for Yourself

The Science of Astronomy

Making Sense of the Universe: Understanding Motion, Energy, and Gravity

Light: the Cosmic Messenger

Formation of the Solar System

Earth and the Terrestrial Worlds

Jovian Planet System

Asteroids, Comets, and Dwarf Planets: Their Nature, Orbits, and Impacts

Other Planetary Systems: the New Science of Distant Worlds

Our Star

Surveying the Stars

Star Stuff

Our Galaxy

A Universe of Galaxies

The Birth of the Universe

Dark Matter, Dark Energy, and the Fate of the Universe

Life in the Universe

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Exam 14: The Bizarre Stellar Graveyard

What do we mean by the singularity of a black hole?

From a theoretical standpoint, what is a pulsar?

Prior to 1991, most astronomers assumed that gamma- ray bursts came from neutron stars (with accretion disks)within the Milky Way Galaxy. How do we now know that this hypothesis was wrong?

Which of the following is closest in mass to a white dwarf?

What is the ultimate fate of an isolated white dwarf?

Briefly describe what you would see if your friend plunged into a black hole.

How does a black hole form from a massive star?

A white dwarf supernova leaves behind

What would happen if a small piece of neutron star material (say the size of a paper clip)struck the Earth?

Which of the following best describes why a white dwarf cannot have a mass greater than the 1.4- solar- mass limit?

Imagine comparing a 1.2 solar mass white dwarf to a 1.0 solar mass white dwarf. Which of the following must be true?

Evidence that Pulsars are Neutron Stars: Suppose a friend of yours insists that pulsars are artificial time- signals constructed by aliens. List and explain all of the observational evidence that pulsars are actually natural phenomena, namely rapidly spinning neutron stars.

A 10 solar mass main sequence star will produce which of the following remnants?

Which statement concerning black hole masses and Schwarzschild radii is not true?

What is an accretion disk?

According to our modern understanding, what is a nova?

Light escaping from white dwarfs will show a gravitational redshift.

What is the evidence that gamma- ray bursts originate from beyond the Milky Way Galaxy?

Which of the following is closest in size (radius)to a neutron star?

What evidence suggests that long gamma ray bursts originate from supernovae of stars massive enough to form black holes?

A Modern View of the Universe

Discovering the Universe for Yourself

The Science of Astronomy

Making Sense of the Universe: Understanding Motion, Energy, and Gravity

Light: the Cosmic Messenger

Formation of the Solar System

Earth and the Terrestrial Worlds

Jovian Planet System

Asteroids, Comets, and Dwarf Planets: Their Nature, Orbits, and Impacts

Other Planetary Systems: the New Science of Distant Worlds

Our Star

Surveying the Stars

Star Stuff

Our Galaxy

A Universe of Galaxies

The Birth of the Universe

Dark Matter, Dark Energy, and the Fate of the Universe

Life in the Universe

Filters